A camera flash unit needs to provide good, relatively uniform illumination of a target surface located some distance (5-7 feet) away from a camera. Prior art camera flash units have a flash light source 6, a reflector 3, and a refractive lens element 8 (see FIG. 1A) to direct light rays generated by the flash light source 6 towards the target surface. In conventional camera flash units of the kind described above, the flash light source 6 is an elongated cylindrical flash lamp tube and the refractive lens element 8 is a condenser lens element with a cylindrical surface 9. That is, surface 9 provides optical power in one plane (for example, Y-Z plane) only. The condenser lens element 8 is used to direct the light from the flash lamp tube towards the intended subject. These camera flash units are relatively wide in a direction Z parallel to the optical axis of a taking lens. More specifically, a conventional condenser lens element 8 of a camera flash unit has to be spaced an appreciable distance d away from the flash light source 6 in order to adequately redirect the light rays emanating from the flash light source. This distance is equal to the back focus of the condenser lens element and is approximately 4 millimeters or larger. Because both the flash light source 6 and the condenser lens element 8 each have a thickness of greater than 1 millimeter, a conventional flash unit can not be made thinner than about 6 millimeters.
U.S. Pat. No. 5,160,192 discloses a flash unit (see FIG. 1B) that includes a reflector 3 composed of a combination of two reflective elliptical shells 4. The optical axes of the shells 4 are separated from one another. A flash light source 6 is located between the shells 4. The light source 6 has a longitudinal axis 7 parallel to the optical axes of the elliptical shells 4. A condenser lens element 8 is a Fresnel lens element and is located at the opening of the reflector 3. This condenser lens element 8 directs the light from the flash light source 6 and the reflective shells 4 towards a target surface. The flash light source 6 is spaced by a relatively large distance d away from the condenser lens element 8. Because of this distance, the width of the camera flash unit disclosed in U.S. Pat. No. 5,160,192 is large.